1. Cook the Pasta: Bring a large pot of salted water to a rolling boil. Add your chosen pasta (rotini or penne) and cook according to package directions until al dente. This usually takes about 10-12 minutes. The pasta should be firm to the bite, not mushy.

2. Drain and Cool the Pasta: Once cooked, drain the pasta thoroughly in a colander. Rinse it under cold water for about 30 seconds to stop the cooking process and cool it down. This prevents the pasta from clumping and keeps the salad fresh. Let it drain well again.

3. Prepare the Chicken and Vegetables: While the pasta cooks, shred or dice your cooked chicken into bite-sized pieces. Chop the romaine lettuce into manageable pieces, halve the cherry tomatoes, and thinly slice the red onion if using.

4. Combine Ingredients in a Large Bowl: In a large mixing bowl, combine the cooled pasta, cooked chicken, chopped romaine lettuce, halved cherry tomatoes, sliced red onion (if using), and 1/2 cup of grated Parmesan cheese.

5. Add the Caesar Dressing: Pour the entire cup of store-bought Caesar dressing over the ingredients in the bowl.

6. Toss Everything Together: Gently but thoroughly toss all the ingredients until everything is evenly coated with the Caesar dressing. Make sure the pasta, chicken, and vegetables are all well-distributed.

7. Stir in Croutons and Season: Just before serving, stir in the croutons. This helps them retain their crunch. Taste the salad and add salt and black pepper as needed. Remember that Caesar dressing is often salty, so season carefully.

8. Serve Immediately or Chill: Serve the salad immediately for the best texture, or cover and refrigerate for at least 30 minutes to allow the flavors to meld and chill thoroughly.